Legendary Resistance (4/Day). If the Demon Lord of Apes fails a saving throw, it can choose to succeed instead.

Magic Resistance. The Demon Lord of Apes has advantage on saving throws against spells and other magical effects.

Magic Weapons. The Demon Lord of Apes’s weapon attacks are magical.

Diseased Ichor. Every time the Demon Lord of Apes takes piercing or slashing damage, a spray of caustic blood spurts from the wound toward the attacker. This spray forms a line 10 feet long and 5 feet wide. The first creature in the line must make a successful DC 24 Constitution saving throw against disease or be infected by the Demon Lord of Apes’s Ichor disease. The creature is poisoned until the disease is cured. Every 24 hours that elapse, the target must make a successful DC 24 Constitution saving throw or reduce its hit point maximum by 5 (2d4). The disease is cured on a success. The target dies if the disease reduces its hit point maximum to 0. This reduction to the target’s hit point maximum lasts until the disease is cured.

Innate Spellcasting. The Demon Lord of Apes’s spellcasting ability is Charisma (spell save DC 22, +14 to hit with spell attacks). The Demon Lord of Apes can innately cast the following spells, requiring no material components:

Immolating Corona. The Demon Lord of Apes’s fiery crown explodes into a burst of yellow-green flames. All creatures within 30 feet of the Demon Lord of Apes take 10 (3d6) fire damage plus 10 (3d6) acid damage, or half damage with a successful DC 24 Dexterity saving throw. If the saving throw fails, the creature also catches fire and takes 3 (1d6) fire damage at the start of each of its turns while on fire. A creature can use an action to extinguish a fire on itself or on another creature within 5 feet.

Frightful Presence. Each creature of the Demon Lord of Apes’s choice that is within 120 feet of the Demon Lord of Apes and aware of it must succeed on a DC 24 Wisdom saving throw or become frightened for 1 minute. A frightened creature repeats the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature’s saving throw is successful or the effect ends for it, the creature is immune to the Demon Lord of Apes’s Frightful Presence for the next 24 hours.

Legendary Actions

The Demon Lord of Apes can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature’s turn. The Demon Lord of Apes regains spent legendary actions at the start of its turn.

Move. The Demon Lord of Apes moves up to half its speed, using any move it wishes.

Burn from Inside. The Demon Lord of Apes targets a creature within 120 feet that has the Demon Lord of Apes’s Ichor disease. The creature takes 10 (3d6) fire damage plus 10 (3d6) acid damage, or half damage with a successful DC 24 Constitution saving throw. If the saving throw fails, the creature also catches fire and takes 3 (1d6) fire damage at the start of each of its turns while on fire. A creature can use an action to extinguish a fire on itself or on another creature within reach.

Spell (Costs 2 Actions). The Demon Lord of Apes casts a spell. Can’t be used twice in the same round.

Fiery Corona (Costs 2 Actions). The Demon Lord of Apes uses Immolating Corona. Can’t be used twice in the same round.

Lair

The Demon Lord of Apes is trapped within the volcano in its island prison. Imprisonment hasn’t prevented the Demon Lord of Apes from mustering an army and turning its confinement into a nightmarish bastion. If the Demon Lord of Apes is encountered in its lair, it has a challenge rating of 28 (120,000 XP).

Lair Actions

On initiative count 20 (losing initiative ties), the Demon Lord of Apes takes a lair action to cause one of the following effects. The Demon Lord of Apes can’t use the same effect two rounds in a row.

The Demon Lord of Apes targets one creature it can see within 120 feet of it, and a fissure full of lava opens under the target’s feet. The target must succeed on a DC 20 Dexterity saving throw or take 28 (8d6) fire damage.

The whole volcano trembles and shakes. Each creature on a solid surface other than a demon must succeed on a DC 20 Dexterity saving throw or be knocked prone. All ground in the volcano becomes difficult terrain for creatures other than a demon until initiative count 20 on the next round.

Volcanic gases form a cloud in a 20-foot-radius sphere centered on a point the Demon Lord of Apes can see within 120 feet of it. The sphere spreads around corners, and its area is lightly obscured. It lasts until initiative count 20 on the next round. Each creature that starts its turn in the cloud must succeed on a DC 15 Constitution saving throw or be poisoned until the end of its next turn. While poisoned in this way, a creature is incapacitated.

The pain of all creatures other than demons within 120 feet of the Demon Lord of Apes is intensified. Until initiative count 20 on the next round, every time a creature affected this way takes damage, he must succeed on a DC 15 Constitution saving throw or be stunned until the end of its next turn.

The Demon Lord of Apes can’t repeat an effect until all have been used, and it can’t use the same effect two rounds in a row.

Regional Effects

The region containing the Demon Lord of Apes’s lair is warped by its presence, which creates one or more of the following effects.

The Demon Lord of Apes can make the volcano erupt at will. A cloud of hot ashes and smoke covers a 6 mile area around the volcano, and magma flows from the volcano’s cone.

When intelligent creatures within 6 miles sleep, they dream with The Demon Lord of Apes. Unless they make a successful DC 15 Wisdom saving throw, they are compelled to seek out and join the Demon Lord of Apes’s cult.

Water within 1 mile of the lair carries the Demon Lord of Apes’s Ichor disease. Any creature that drinks the water must make a successful DC 15 Constitution saving throw against disease or be infected. An infected creature is poisoned until the disease is cured. Every 24 hours that elapse, the target must repeat the saving throw. On a failure, its hit point maximum is reduced by 5 (2d4). The disease is cured on a success. The target dies if the disease reduces its hit point maximum to 0. This reduction to the target’s hit point maximum lasts until the disease is cured.

When the Demon Lord of Apes dies, all these regional effects fade immediately.

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